The present invention relates to a vessel or reactor for the treatment of fluid substances, especially a vessel or reactor for fluid substances of the type which is equipped with a stirring system and has a lined inner surface.
So-called reactor vessels for the mixing and/or reaction of fluid substances, which may or may not have a solid and/or gaseous phase, have been widely known hitherto. Such vessels or reactors are widely used in the chemical industry for the preparation of chemical substances which are produced after stirring or reaction of other substances. Such reactor vessels have a preferably pressure-tight tank made of metal, in which a number of fittings and devices are installed for processing the substances contained therein as well as for monitoring and controlling the preparation process. Such devices typically include a stirrer, which is mounted inside the vessel in various positions, for example with a vertical or inclined axis, coaxially with the vessel or eccentrically, one or more baffles, which are fixed to the vessel walls to increase the intermixing of the substances during the stirring operation, immersion pipes for feeding in process materials or for removing products, temperature-measuring devices for the mixture, pressure-measuring devices for the tank internal pressure, and so on.
For applications using chemically very aggressive substances, such as acids and like substances, the tank and all the above-mentioned additional devices are lined or coated with an acid-resistant material. Lining with glass enamel, ceramic enamel or the like is typically preferred in view of its practical applicability and reliability. For that reason, for such applications all the surfaces of the apparatus and of the associated devices that come into contact with the mixture are coated with the above lining.
That structural solution has a first disadvantage, however, that the tank and the associated additional devices integral with the tank, once lined with the above-mentioned surface treatment, can no longer be modified or removed in order that the continuous surface of the above-mentioned lining be not broken. That disadvantage is particularly serious when it is necessary for process-related reasons to make modifications to the reactor and the fittings integral therewith or to add further fittings. For example, it could be necessary to change the number, the arrangement or the shape of the baffles. It could also be necessary for an internal component that is vibrating or is being excessively stressed by the action of the stirrer to be secured to the vessel wall.
A second disadvantage presented by the monolithic structure of the vessel with its fittings is the necessity to re-enamel the entire apparatus even if the enamelled lining of only one of its fittings has been damaged.
The re-enamelling cannot be carried out on-site; because it is a very special process, which consists of a plurality of baking operations in special ovens at temperatures of about 900° C., it is necessary to return the apparatus to the manufacturer, which involves a great deal of expense for demounting from the plant and for shipping as well as loss of production.